The present invention relates to a display device suitable for connection to a computer etc., and particularly to a display device having a power management function.
Generally, current display devices have a power management function of for reducing consumption of power to realize power savings. Functions of power management are standardized by Energy Star program by the United States Environmental Protection Agency, Video Electronics Standards Association, Swedish National Board for Industrial and Technical Development, etc. Also, there are many disclosed patent applications about power management. For example, Japanese Patent Application Laid-Open No. 58-99075 (1983) and Japanese Patent Application Laid-Open No. 1-177076 (1989) disclose techniques for ON/OFF controlling power supply to a CRT monitor by detecting-synchronizing signals from a video signal generator, and Japanese Patent National Publication of the Translation No. 8-508831 (1996) and Japanese Patent Application Laid-Open No. 6-110396 (1994) disclose in detail techniques for realizing energy saving in two or more control levels. In the techniques disclosed by the former two references, energy saving in a display device is realized in the absence of synchronizing signals when the computer is being used; in the techniques disclosed by the latter two references, two or more energy saving modes are realized according to the combination of absence/presence of synchronizing signals.
FIG. 5 is a block diagram showing the structure of a portion related to the power management of a conventional display device. As shown in FIG. 5, this display device 9 has signal detecting means 2, image display means 3, power management signal output means 4, power reduction means 6, power management ON/OFF signal detecting means 10 and an image output portion 20. The image output portion 20 is constructed as a cathode ray tube (CRT).
In the display device 9, as shown in FIG. 6, the power management modes include predetermined modes: Level 1 to Level 3. The display device 9 selectively realizes any of these modes on the basis of the combination of horizontal and vertical synchronizing signals sent from the computer 1. That is to say, fixed modes are realized according to the combination of horizontal and vertical synchronizing signals.
For example, in the technique described in the above-cited Japanese Patent National Publication of the Translation No.8-508831, page 7, column 14, line 39 to page 8, column 15, line 2, several kinds of power reduction modes are determined in correspondence with combinations of presence/absence of horizontal synchronizing signal, vertical synchronizing signal and video signal sent from a computer etc., according to which consumption of power is lowered in several ways.
Referring to FIG. 5 again, when the computer 1 sends a combination of synchronizing signals which corresponds to a certain power management mode, the signal detecting means 2 detects this combination and sends it to the power management signal output means 4. On the basis of the combination of synchronizing signals sent from the signal detecting means 2, the power management signal output means 4 specifies the mode and sets power reduction in that mode. This technique is disclosed in Japanese Patent National Publication of the Translation No.8-508831, page 8, column 16, lines 26 to 44, for example.
The power reduction means 6 operates on the basis of instructions from the power management signal output means 4. As a result, the display device 9 changes from normal operation mode to a power management mode defined by the combination of the synchronizing signals. The operator 7 only selects ON/OFF of the power management operation by using OSD (On Screen Display) displayed on the screen 30 of the image output portion 20, for example.
The conventional display device configured to thus operate has the following problems.
Firstly, the display device realizes fixed power saving modes in accordance with individual combinations of signals sent from the computer etc., so that the user (operator) cannot freely select or set the power saving mode on the display device, which results in wasteful consumption of power.
Secondly, fixed voltages are applied to the heater in the image output portion 20 (i.e. CRT heater) in accordance with consumed power and recovery time (i.e. the time taken to enable the screen 30 to display an image when the power management operation is canceled) and the user cannot freely select the consumed power and recovery time in the power saving mode on the display device, resulting in consumption of wasteful power.
The present invention has been made to solve the problems above, and an object of the invention is to provide a display device which allows an operator to freely set a mode to suppress wasteful power consumption.
According to a first aspect of the present invention, a display device which displays an image on a screen in an image output portion on the basis of a received video signal comprises: power reduction means configured to reduce, in a plurality of modes, power supplied to a device component included in said display device; power management output selecting means configured to make a setting to any of said plurality of modes on the basis of a selection made by an operator; signal detecting means configured to detect a trigger signal; and power management signal output means configured to give an instruction to said power reduction means in response to detection of said trigger signal by said signal detecting means to perform said mode defined by said setting.
In accordance with the display device of the first aspect of the invention, power management operation (power saving operation) is realized in a mode selected by the operator. This suppresses consumption of wasteful power.
According to a display device of a second aspect of the invention, in the first aspect, the display device further comprises means configured to display said plurality of modes for selection on said screen in the form of on screen display and said power management output selecting means makes said setting according to which of said plurality of on-screen-displayed modes said operator has selected.
In accordance with the display device of the second aspect of the invention, the operator can select a desired mode from among a plurality of modes displayed in the form of on screen display (OSD), so that he/she can easily and correctly set the mode without a mistake.
According to a display device of a third aspect of the invention, in the second aspect, said device component includes a plurality of unit components and said means configured to display said plurality of modes in the form of on screen display displays items which can be selected individually for each said unit component as said plurality of modes on said screen in the form of on screen display.
In accordance with the display device of the third aspect of the invention, power saving operation can be selected for each unit component, so as to flexibly meet stricter power saving requirements.
According to a display device of a fourth aspect of the invention, in the first aspect, said image output portion is a cathode ray tube having a heater and said device component includes a CRT heater circuit configured to supply power to said heater, and wherein said plurality of modes include a mode in which supply of power to said heater is kept on.
In accordance with the display device of the fourth aspect of the invention, the mode of continuing supply of power to the heater of the cathode ray tube can be selected so that the image display can be reactivated immediately after the power management operation has been canceled.
According to a display device of a fifth aspect of the invention, in the first aspect, said signal detecting means monitors a horizontal synchronizing signal and a vertical synchronizing signal accompanying said video signal and detects as said trigger signal a state in which at least one of said synchronizing signals is not being received.
In accordance with the display device of the fifth aspect of the invention, operation changes from normal mode into power management mode in the absence of any of the horizontal and vertical synchronizing signals, so that the display device can be used as they are with external devices, e.g. a computer, which are used in connection with conventional display devices having power management function.
These and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.